Compact telephoto type zoom lens

ABSTRACT

A COMPACT TELEPHOTO ZOOM LENS IS PROVIDED COMPRISING A ZOOMING SYSTEM COMPOSED OF THREE GROUPS OF CONVERGING, DIVERGING AND CONVERGING LENSES FROM THE SIDE OF THE OBJECT, AND A RELY LENS SYSTEM CONNECTED TO SAID ZOOMING SYSTEM. THE RELAY LENS SYSTEM IS COMPOSED OF TWO GROUPS, A FRONT GROUP AND A REAR GROUP, WHICH IS CHARACTERIZED BY CARRYING OUT THE CONVERSION OF THE MAIN FOCAL LENGTH   BY MOVING THE SECOND GROUP OF THE ZOOMING SYSTEM RADIALLY, AND CORRECTING THE DEVIATION OF THE IMAGE CAUSED BY SAID MOVEMENT BY THE MOVEMENT OF THE THIRD GROUP.

COMPACT TELEFHOTO TYPE ZOOM LENS Filed June 26, 1968 2 Shoots-Shoot 1 /4.s if F I /e Ffm-# ETT -o.s 0.5 i *V- SPHERICANBERRATION SINUSOIDAL CONDITION 1010 L l 6.82' 4.s2

STT To? "3? '35 .5

ASTIGMATISM FIG. 3

. KV", SR We Oct. 26, 1971 TAKAsHn Husum-u ETAL 3,615,125

COMPACT TELEPHOTO TYTF '11.OOM LENS Filed June 2e, 1968 z shoots-sheen n FIG. 4

cHRoMATlgFABr-:RRATICN MAeNlFlCATloN l(g une) FIG. 5

DISTORTION United States Patent O 3,615,125 COMPACT TELEPHOTO TYPE ZOOM LENS Takashi Higuchi, Yokohama-shi, and Soichi Nakamura, Tokyo, Japan, assignors to Nippon Kogaku K.K., Tokyo, Japan Filed June 26, 1968, Ser. No. 740,168 Claims priority, application Japan, July 4, 1967, 42/ 42,564 Int. Cl. G02b 15/14 U.S. Cl. 350-184 2 Claims ABSTRACT F THE DISCLOSURE A compact telephoto zoom lens is provided comprising a zooming system composed of three groups of converging, diverging and converging lenses from the side of the object, and a relay lens system connected to said zooming system. The relay lens system is composed of two groups, a front group and a rear group, which is characterized by carrying out the conversion of the main focal length by moving the second group of the zooming system axially, and correcting the deviation of the image caused by said movement by the movement of the third group.

This invention relates to a compact telephoto type zoom lens comprising a zooming system composed of three groups of converging, diverging and converging lenses from the side of the object, and a relay lens system composed of two groups, a front group and a rear group, connected to said zooming system, which is characterized by carrying out the conversion of the main focal length by moving the second group of the zooming system, the movement of an image position caused by the deviation of the second group of the zooming system being corrected by the movement of the third group of the zooming system, providing a converging lens composed of positive and negative lenses cemented to each other behind the single positive lens in the rst group, providing a diverging lens composed of positive and negative lenses cemented to each other and a single negative lens behind said diverging lens in the second group, providing a single positive lens or a compound converging lens composed of positive and negative lenses cemented to each other depending on the degree of achromatism to be desired in the third group, having the front group of the relay lens system composed of at least two groups of three lenses, and having the rear group composed of four lenses in at least three converging, diverging and converging groups.

The object of this invention is to provide a telephoto type zoom lens having excellent performance throughout the Whole zooming range while making the whole system compact, wherein the zooming system is composed of three groups of converging, diverging and converging lenses, and the third group is moved in such a manner that the position of animage can be kept constant when the second groupis moved axially.

In planning a telephoto zoom lens for a still camera, it is required that the whole system should be made as compact and light as possible. It is an indispensible factor to minimize the zooming system in order to malte the whole system compact. Generally speaking, when the zooming system is made smaller, an increase of the aberrations results so that correction of astigmatism and chromatie aberration of spherical aberration requires a high technique for correction.

As the relay lens which can overcome the increase of the astigmatism caused by the zooming system, and has less spherical aberration, a system of Petzval type can be thought about, but when such a system as Petzval system 3,615,125 Patented Oct. 26, 1971 is adopted it is apt to increase the whole length of the system when compared with the focal length; and when such a system as Petzval system is used as the relay lens system, it is not appropriate in view of the condition that the whole system should be made compact. As to the compact relay lens, it is preferable to make the telephoto ratio as small as possible, and at the same time having the function to eliminate astigmatism and all other abberation.

In accordance with this invention, it is possible to provide a compact relay lens in which astigmatism and spherical aberration caused by zooming system can be excellently corrected.

In accordance with this invention, when the maximum focal length of the whole system is set to be fL and the whole length including the back focus is set to be D, such a relation as D fl can be attained and it is possible to obtain a very compact and light weight telephoto zoom lens having high performance wherein aberrations are excellently corrected. This invention can be applied not only to still cameras, but may also be used for zoom lens for printers, cine-cameras, or zoom lens for projectors, extending the usefulness of zoom lens.

In accordance with this invention, a telephoto zoom lens system is provided comprising a zooming system composed of three groups of converging, diverging, and converging lenses in seriatim from the object side, and a relay lens system connected to said zooming system composed of the two groups of lenses. In the first group, a converging lens prepared by cementing positive and negative lenses is provided behind a single positive lens, and in the second group a diverging lens prepared by cementing alternate positive and negative lenses is provided before a single negative lens. A third group is provided composed of a single positive lens, or a compound converging lens prepared by cementing positive and negative lenses depending on the degree of the achromatism to be desired. The relay lens which is connected to said third group, is composed of two lens groups, i.e., a front group composed of at least two groups comprising three lenses, and a rear group composed of four lenses in at least three groups each group in its respective order being converging, diverging and converging.

When the focal length of the rst group is set to be f1, and the focal length of the second group is set to be f2, and the radius of curvature of the rst surface of the second group is set to be R6, and the focal length of the front group of the relay lens is set to be fm1, and the refractive indexes of the positive lens and the negative lens of the converging cemented lens of the front group of the relay lens are respectively set to be 111 and n2, and the focal length of the whole relay lens is set to be fm, and the radii of curvature of the front surface and the rear surface of the last positive lens are respectively set to be REL and Rb, the following conditions must be satisfied.

The Formula 1 shows the basic condition for reducing astigmatism and spherical aberration caused by the zooming system while keeping the relay lens system very compact.

In the Formula (a) of the Formulae l, when fmf becomes larger than 1.1 fm, the whole length of the relay lens system becomes too long, and as a result, the whole length D of the whole system becomes larger than the maximum Afocal length fl which departs from the spirit of this invention. When it becomes'smaller than 0.8 fm, the relay lens itself becomes a lens having a very small telephoto ratio, and the correction of aberration becomes very dicult and impractical.

retain the atness of the image when the relay lens is required to cover more than 20 of the total angle of view. In other words, it is possible to easily correct the distortion by means of the condition of Formula 3 without dis- In the Formula (b) of (l), when ft2-n1 becomes 5 turbing the balance of the other aberrations. smaller than 0.1, the correction of astigmatism is still The Formula 4 shows the basic relation between the difficult, even if the Formula (a) of (l) should be satiszooming system and the relay lens, and when fl/fm befied. Only when the conditions of (a) and (b) are satiscomes smaller than 0.7, the zooming system becomes too ed simultaneously minimum aberration correction can be small, and the correction of aberration becomes too difexcepted. 10 cult and impractical. On the other hand, when fl/fm is The upper limit of the Formula (b) ls close to the limit larger than 1.8, the correction of aberrations can be easily of the difference of the refractive index of the conven- Gamed Ollf- HOWeVer? the s1ze of the 'whole SYStem b etional optical glass. It is impossible to obtain the dif- Comes t00 large all@ 1t 1S HO'PfaCtlCal 1 I1V16VV-Of the Silll ference of refractive index above that from the conven- Camera Which e55136613115 fequlfes OPefaIOYlablhtY- tional optical glass, and a deterioration of spherical abcr- 1D As is apparent from the above explanations, when the ration results. conditions represented by the Formulae 1 to 4 are satisfied, The condition represented by the Formula 2 prevents the whole length D becomes smaller than the maximum the distortion on the shorter focal length from becoming focal length flj and this it is possible to realize a comnegative. At the same time, it is a condition for keeping pact telephoto zoom lens having high performance. the balance of the image on both ends of the zooming 20 This invention will be described more clearly referring Zone. In other words, when R6 becomes eo or negative, to the illustrative embodiments shown in the attached the distortion becomes too much in the negative on the drawing, in which: shorter focal length side, and the difference between the FIG. 1 is a cross sectional view of a zoom lens for still same and the distortion of the longer focal length side camera according to this invention; and becomes too great. On the other hand, when R6 becomes D FIGS. 2 through 5 are graphs of aberrations at the minismaller than l0 lf2! the distortion on the side of the shorter mum, intermediate, and maximum focal length of the focal length can 'be prevented from becoming negative, embodiment shown in FIG. 1. but it becomes diicult to keep the balance of the images The following examples correspond to the embodiment on the side of shorter focal length and longer focal length. no illustrated in FIG. 1. Therefore, R5 must be within the range defined by the o In the followlng examples, ,.b ,.2 ,25 are the radll Formula 2. of curvature of the respective lenses, and d1, d2 124 The Formula 3 represents the condition for overcoming are the central thickness of the respective lenses and the the positive distortion which is caused when the front air-spaces, and nl, n2 U15 are the refractive indexes group of the relay lens is required to be bent in the con- 35. on line d of the respective glass materials, and v1, v2 Vex direction toward the surface of an object in order t0 v15 show the Abb numbers of the glass materials.

EXAMPLE 1 [f=80-200.3 F/4.5 Whole length=l95.31, the maximum focal length=200.3]

d1=5.o m=1.62041 vi=60.3 r2=3s1.11o

d2=0.1 f1=121.0.-- rt=135.630

d3=7.3 n1=1.61375 t-2=56.3 r1=156.o00

l4=2.0 m=1.75520 v3=27.5

rs=10000.000 dt=3.7

ni=1ss93 v1=31.1 r7=-44.55o d1=1.0 1 5F08 69 6 7L U 2=403 r8=49-g24 5:44, 5 l 5 'rla=1.62041 v6=60.3 n0=140.585 dw=39.40-1.04

r11=l2l.500 d11=40 1 69041 60 3 717: t) fG-ms rip-51.315 d=1.o 7

' m=1.62004 va=36.3 11F-148.009 di3=1o.88-1o.99

m=1.54s14 1=45.9 f 1 7 8 r15=l347294 d15=07 l ri-32Go() d15=10.4 m0=1.53172 v10=48.9

rlp-222.200

du=2.s mi=1.7s470 vn=26.1 r18=44.818

dt5=3a1 ri=103.461

d=3.8 m2=1.51680 v1.=64.2 [nt-1124i r2o=63360 d21=1.5 n1t=1.7440o v13=44-9 T2:=40.000

d22=4.9 Hur-1.60895 U14=30.0 T23- fluent r :aus

du4=LU lti5=l.7Ul5\l biLLl T25=2U85243 B.i=4o.u

EXAMPLE 2 According to the present invention, a high quality zoom lens is obtained which is very compact and excellently 40 corrected. The zoom lens of this invention may be used not only for still cameras but also for eine cameras and for printers, which extends the use of zoom lenses.

What is claimed is:

1. Telephoto zoom lens comprising a zooming system composed of three groups of converging, diverging and converging lenses in seriatim from the object side, and a relay lens system connected to said zooming system composed of two groups of lenses, a front group and a rear group, which is characterized by carrying out the conversion of the main focal length by moving the second group of the zooming system axially and correcting the movement of the image position caused by the movement of the second group of the zooming system with movement of the third group; the rst group including a converging lens prepared by cementing positive and negative lenses and disposed behind a single positive lens, the second group including a diverging lens prepared by cementing positive and negative lenses with a single negative lens behind said diverging lens, the third group including a compound converging lens prepared by cementing positive and negative lenses; the front group of the relay lens system including at least two groups of three lenses in which one group is formed by cemented positive and negative lenses and the rear relay group includes four lenses in at least three converging, diverging and converging groups; and having the following numerical values wherein f subscript designates the focal lengths of the respective lens groups, r subscript the radii of curvature of the respective lenses, d subscript the central thicknesses and air spaces, n subscript the refractive indices., and v subscript the Abb numbers:

2. Telephoto zoom lens comprising a zooming system composed of three groups of converging, diverging and converging lenses in seriatim from the object side, and a relay lens system connected to said zooming system composed of two groups of lenses, a front group and rear group, which is characterized by carrying out the conversion of the main focal length by moving the second group of the zooming system axially and correcting the movement of the image position caused by the movement of the second group of the zooming system with movement of the third group; the first group includingl a converging lens prepared by cementing positive and negative lenses and disposed behind a single positive lens, a second group including a diverging lens prepared by cementing positive and negative lenses with a single negative lens behind said diverging lens, the third group including a single positive lens; the front group of the relay lens System including at least two groups of three lenses in which one group is formed by cemented positive and negative lenses and the rear relay group includes four lenses in at least three converging, diverging and convergingl groups; and having the following numerical values wherein f subscript designates the focal lengths of the respective lens groups, r subscript the radii of curvature of the respective lenses, a' subscript the central thicknesses and air spaces,

30 n subscript the refractive indices, and v subscript the Abb numbers: i

[/=80.2-201.2 F/5.6 Whole length=182.02, the maximum focal lei1gth=201.2]

di=4.0l n :1.62041 I7 =60.3 r2=3oz266 l 1 d2=0.08 fi=97.5 T3=109.370

d3=5.93 m=161375 U2=56.3 T4=l25.814

d4=1.60 7L3=L75520 U3=275 T5=288150 d5=0.87-33.68 rg=815.033

da=3.01 m=168893 U4=3L1 =35.890

d7=0.80 17,5=1.51728 115=69.6 f 32,5 rs=40.129

dg=3.51 n=-36.473

' dg=1.00 rl=l.62041 U=60.3 10=103.3v08

dm=33.81-0.82 T11=82.459 f3=87.2 dii=401 717:1.51680 U1=642 A T12=97.968

d12=8.69-8.87 Ti3=31-005 di3=4.73 7La=1.548l4 tg=45.9 Ti4=1350.662

F052 fm1=122.24. T15=34.195

d15=10.43 7Ln=154771 U9=62.9 T1a=100A38 di4=2.81 IL10=1.78470 Uio=26.1 T17=48.875

d11=3769 T1g=103.719

d1g=3.81 '/Li1=1.51118 vn=50.9 T19=63.518 fm=113.2- d19=3.01

d2o=1.52 lli2=1.74400 11i2=44.9 r21=42.105 v d21=4.89 m3-11.69895 v13=30.0

d23=4.01 '7L|4=1.70154 Di4=4L1 r24=275.045

References Cited UNITED STATES PATENTS 2,937,572 5/1960 Yamayr 350-184 3,336,094 8/1967 Macher 350-184 JOHN K. CORBIN, Primary Examiner U.S. Cl. X.R. 

